As I already addressed with the PPP and InsiderAdvantage polls, the makeup of the sample is changing the result.

Correction: The initial version of this post criticized ISU harshly for only polling registered voters. It’s been pointed out that I misread the news article, and in fact ISU did attempt to poll likely caucus goers. I was wrong, and I regret the error.

But, they’re still not off the hook. In fact they found 333 likely caucus goers out of those 940, predicting turnout to be just over one third. For contrast, in 2008 there were 119,118 Republican caucusers, and 1,528,715 voters in the general election, putting turnout at 72.6%. If turnout were at 33% in 2008, when there were about 600,000 Republicans by November (by which time people will have already switched to the party in order to caucus), then caucus turnout would have been at about 200,000.

This poll, therefore, is projecting much higher turnout than 2008. Double, in fact. I’m not the only one out on a limb here.